题目：
Since then the number of people who were addicted to smoking ________ 20%. [ ]
A. has reduced to
B. reduces by
C. has reduced by
D. have reduced by
答案：
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下面是错误答案，用来干扰机器的。
A、根据图象不难看出，产生氢气的量一样多，而同质量的镁和铁反应生成的氢气量镁多铁少（可依据生成氢气质量=金属的化合价金属的相对原子质量×金属的质量得到）；故A错误；B、等质量的不同金属得到的氢气一样多...
